The impact of acute hypothyroidism on lipid levels in athyreotic patients

We investigated the effect of acute hypothyroidism on lipid concentrations especially on high density lipoprotein (HDL-cholesterol) level in athyroatic patients. Materials and Methods: Thirty-one patients, with a history of differentiated thyroid carcinoma and total thyroidectomy, who were candidates of radioiodine therapy, enrolled in the study. Their lipid profiles and serum thyrotropin stimulating hormone (TSH) levels were measured before and two-to-six weeks after thyroid hormone withdrawal. The lipid concentrations were compared with the paired t test and serum TSH using the Wilcoxon singed rank test. P values < 0.05 were considered statistically significant. Results: The median of TSH concentration was 0.06 mU / liter on thyroid hormone suppressive therapy and 102 mU / liter at the thyroid hormone withdrawal phase (P < 0.0001). The serum concentrations of all lipids were significantly increased after withdrawal (P < 0.0001). The mean (SD) of the HDL-cholesterol concentration rose from 44 ± 9 mg / dL to 58 ± 17 mg / dL. The levels of total cholesterol, LDL-cholesterol, HDL-cholesterol, and triglyceride increased by 58, 75, 30, and 59%, respectively, during acute hypothyroidism. Conclusion: The present study showed that thyroid hormone withdrawal altered the lipid concentrations significantly, in a short period of time. The levels of both atherogenic (LDL-cholesterol) and cardioprotective (HDL-cholesterol) particles increased concurrently. Their clinical importance should be investigated in future.